Printing systems, such as high demand printing systems, consume large volumes of paper. When paper trays are loaded or filled in a feeder system attached to a printing system or other media handling system, the stacks of media are often loaded in an unregistered state. As an operator loads each successive grouping of media, e.g., a ream of paper, alignment offsets are created in the stack that can lead to feed problems due to shifts in the top sheet process position, i.e., the uppermost sheets of media. FIG. 1 broadly depicts feeder system 10 comprising elevator tray 12, trail edge guide 14 and feed head 16. As is well known in the art, feed head 16 may take various forms, for example, a vacuum feed head or a friction feed head. During media loading, some reams of media are disposed closer to the trail edge position or in other words trail edge guide 14, i.e., reams 18a and 18b, while other reams of media are disposed closer to the feeding position or in other words feed head 16, i.e., reams 20a and 20b. Due to the offset of the position of top sheet 22 relative to feed head 16, top sheet 22 may not enter the printing system (not shown) in its predicted manner thereby entering later than expected or in a skewed orientation, for example. Such a condition is commonly referred to as a mis-feed.
Moreover, the weight of media stacked in a feeder system subjects the trail edge guides to forces that often deflect the guide from its typical vertical orientation. Such deflection causes the top sheet lead edge/process feed location to be altered, which in turn leads to increased feeder shutdowns, i.e., mis-feeds and/or multi-feeds. FIG. 2 broadly depicts feeder system 10 comprising elevator tray 12, trail edge guide 14 and feed head 16. Again, during loading, some reams of media are disposed closer to the trail edge position, i.e., reams 24a and 24b, while other reams of media are disposed closer to the feeding position, i.e., reams 26a and 26b. In this example, it can be see that the lateral force imparted by ream 24a on guide 14 changes the position of guide 14, i.e., deflects guide 14 from it typical vertical position by angle α. Such deflection further amplifies the aforementioned stacking alignment issues. Thus, as elevator tray 12 lifts the reams of media, the unregistered alignment of the various reams of media can cause top sheet 28, located at the top sheet process position, to be so misaligned relative to the sheets below that feed head 16 not only feeds top sheet 28 but also simultaneously feeds the sheet or sheets just below top sheet 28. Under such conditions, a vacuum port (discussed in greater detail infra) of feed head 16 is exposed to the sheet or sheets below top sheet 28, thereby drawn up more sheets than just top sheet 28. Such a condition is commonly referred to as a multi-feed. Additionally, it should be appreciated that deflection of the trail edge guide can lead to interferences with parts of the feeder system, such as a frame or feeder tray during loading and unloading operations.
A variety of devices have been utilized to prevent the foregoing failure modes. For example, complex spring loaded “pushers” have been placed in the trail edge region and arranged to apply a lateral force against a plurality of sheets of media thereby forming an aligned stack of media. Although these devices may temporarily align the media relative to each other, upon application of air flow from a “fluffer”, described in greater detail infra, the previously aligned sheets may become misaligned. For example, air directed opposite the process direction is sometimes introduced near the feed head to aid in the separation of sheets for purposes of proper feeding. As air is introduced opposite the process direction, sheets may be pushed back away from the feed head, thereby further compounding the issue of misalignment between the top sheet and the sheets below. This condition may also push the top sheet back so far that it fails to load at the proper time, thereby resulting in a mis-feed.
The present disclosure addresses an apparatus for ensuring that media in the top sheet process position is aligned in such a way as to prevent the occurrence of mis-feeds and multi-feeds thereby maximizing printing system performance and throughput.